Antenna using end fire elements, translatable or tiltable apart or together, to control beam width



June 21, 1966 w. A. SCHNEIDER 5 ,6 ANTENNA USING END FIRE ELEMENTS. TRANSLATABLE OR TILTABLE APART 0R TOGETHER, TO CONTROL BEAM WIDTH Filed July 6, 1964 2 Sheets-Sheet 1 l i r INVENTOR, WILHELM A. SCHNEIDER.

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June 21, 1966 w. A. SCHNEIDER 3,257,660 ANTENNA USING END FIRE ELEMENTS, TRANSLATABLE OR TILTABLE APART OR TOGETHER, TO CONTROL BEAM WIDTH 2 Sheets-Sheet 2 Filed July 6, 1964 INVENTOR,

WILHELM A. SCHNEIDER.

United States Patent 3,257,660 ANTENNA USING END FIRE ELEMENTS, TRANS- LATABLE OR TILTABLE APART 0R TOGETHER, T0 CONTROL BEAM WIDTH Wilhelm A. Schneider, Fair Haven, NJ., assignor to the United States of America as represented by the Secretary of the Army Filed July 6, 1964, Ser. No. 380,714 7 Claims. (Cl. 343-758) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

The present invention relates to an antenna array of unidirectional radiators and more particularly to an antenna array having means for providing a multiple of different radiation patterns and variable beamwidths by simple mechanical adjustments.

Those concerned with the development of directional antenna arrays have long recognized the need for a variable beamwidth antenna using only simple mechanical means for 'varying the etfective aperture of the array while providing a multiple of radiation patterns. The present invention fulfills this need by providing a plurality of variable beamwidth antenna elements mounted in an array and having a relatively simple inexpensive means for varying the orientation of the elements with respect to each other.

The exact nature of this invention and other advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawings, in which:

FIG. 1 shows an oblique view of the preferred embodiment of the invention;

FIG. 2 shows an endview of a portion of the apparatus shown in FIG. 1;

FIG. 3 shows a section of the apparatus taken on the line 3-3 of FIG. 2; and

FIGS. 4-6 show diagrammatic views of the apparatus with different orientations of the antenna elements.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIG. 1 an antenna array 11 comprising a plurality of like unidirectional antenna elements 12 mounted on a pedestal 13. Antenna elements 12 each include an elongated rod 14 of rigid dielectric material having a hollow dielectric tube 15 slidably mounted thereon with a helical radiator .16 (FIG. 2) wound on the distal end thereof. Also mounted on rod 14 is a metal ground plane 17. The specific construction of antenna elements 12 is more fully disclosed in co-pending application Serial No. 236,460, filed on November 8, 1962 by Kurt Ikrath and Wilhelm A. Schneider. The construction and radiation characteristics of antenna elements 12 are also discussed in Antennal Innovation Glass- Fi'ber, Electronics, September 21, 1962, pp. 44-47, by K. Ikrath and W. Schneider.

Mounted on pedestal 13 is a positioning means '18 having a pair of parallel positioning plates 19 rigidly supported by a spacer 21. Extending from and supported between plates 19 is'an arm 22 pivotally connected by pivot pin 23 to yoke 24. A base plate 25 rigidly attached to yoke 24 is rotatably mounted on pedestal 13.

Each support plate 19 comprises four elongated radial slots 26. Each radial slot 26 on one plate 19 is coextensive with a separate one of the radial slots 26 on the other plate 19. The distal faces of plates 19 are recessed to provide a circular flange 27. Two camming plates 28 each having four spiral slots 29 are each inset in the recess on plate 19 and are rotatably supported by flange 27. The centers of plates 28 and 19 and spacer 21 have a coextensive bore 30 extending therethrough.

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The five antenna elements 12 are arrayed with the proximal ends of the rods 14 supported by positioning means 18. The center element 12 of the array has its rod 14 slidably positioned in bore 30. The four outer elements 12 are symmetrically spaced around the center element 12 with the free ends of rods 14 on each element extending through a separate one of each of the spiral and radial slots in camming plates 28 and support plates '19 respectively. Each radiator 16 may be energized by a coaxial line (not shown) with the center conductor feeding the radiator 16 and the outer conductor connected to ground plane 17.

The operation of the array will now be described. Each antenna element 12 will be dimensioned such that the helical radiator 16 will operate in the axial mode. The beam radiated from element 16 will be guided by tube 15 causing the beam to become narrower. The resulting beamwidth will depend on the effective length of tube 15 which may be varied by sliding tube 15 on rod 14. In other words, the effective aperture of each element 12 has a maximum diameter when the tube is positioned to the right as shown in FIG. 3. As the tube 15 is moved to the left the effective aperture of each element becomes smaller resulting in a wider beamwidth. The effective aperture of the composite array will be equal to substantially the sum of the individual effective apertures of each element. Of course, as the effective aperture of an antenna system increases while the wavelength remains constant the resulting beamwidth becomes narrower. This follows from the generally accepted principle that beamwidth is inversely proportional to aperture width. While tube 15 may vary the effective aperture of each antenna element 12, the effective aperture of the entire array may be varied by moving each element closer together and further apart. It can be seen, that as camming plates 28 are rotated, rods 14 will slide radially in slots 26. For example, starting from the position shown in FIG. 1 with all elements 12 parallel, a converging orientation of elements 12 may be established by rotating only the front camming plate 28 clockwise. A diverging position could have been established by rotating only the rear camming plate 28. Rotating both camming plates the same amount would keep the elements 12 parallel but bring them closer together.

The coaxial feed lines (not shown) may be mounted in rods 14 and extend from the free ends thereof. Depending on the desired use, all elements may be fed in parallel and in phase or out of phase. The center element 12 may be used for receiving while the outer elements 12 are used for transmitting. Also, the center element 12 may be the only element energized with the outer elements acting as parasitic elements. 'Of course, with all elements 12 energized greater power outputs are obtained.

FIGS. 4, 5, and 6 show some variations of the positions which the array may assume by simply rotating the camming plates 28. In FIG. 4 the antenna elements 12 are paralleled and spaced a distance such that the effective apertures 31 are separated. FIG. 5 shows the elements 12 being parallel but spaced a distance wherein the effective apertures 31 overlap. FIG. 6 shows the elements '12 diverging and with the effective apertures 31 at an angle to each other. The resulting beamwidth and patterns produced by the array in these positions may be generally analyzed by considering the sum of the effective apertures of the individual elements which in effect produce the efl ective aperture for the array.

The effective aperture of the array may be considered to extend out to the extremities of the individual apertures 31. In FIG. 4 the aperture of the array may be looked at as a partially illuminated aperture having dis- 3 continuities. Depending on the beamwidth of the individual elements 12 the resulting beam of the array will be either a split beam or a notched beam. Of course, the beamwidth of the individual elements 12 may be varied by sliding the tube 15 on rod 14. The array may, therefore, be adjusted, to a position where the individual element beamwidths are at a minimum and the apertures 31 spaced a maximum distance, to produce a multiple or split beam pattern for the array. As the beamwidths of the elements are widened by sliding tube 15 the beams will merge and produce a notched beam.

The elements 12 may also be brought closer together to position shown in FIG. 5. Here, the effective aperture of the array is substantially fully illuminated but the aperture width of the array is a minimum. Therefore, there will be a single beam which will have a relatively wide beamwidth. Of course, the beamwidth may be made even wider by sliding tube 15 to the left as viewed in FIG. 1 to reduce still further the width of the effective aperture of the array.

The narrowest beamwidth for a single beam from the array is obtained with some optimum setting somewhere between the extreme positions shown in FIGS. 4 and 5. Such a position should be a compromise between a maximum effective aperture for the array and the least amount of discontinuities or in other words with substantially full illumination of the array aperture.

As shown in FIG. 6, the elements 12 may be set in a diverging position. Obviously, a converging position may also be obtained as explained above. Such positions may be used to provide numerous variations of beam patterns. However, the position shown in FIG. 6 demonstrates a method of obtaining a substantially planar wavefront. When all elements 12 are parallel the wavefronts for a single beam are not exactly planar. This is true of any array using finite radiators since perfectly parallel rays are impossible to obtain from the individual radiating elements which make up the array. It has been found with a single beam pattern that to slightly diverge the elements 12 as shown in FIG. 6 tends to make the normally diverging rays at points P parallel without effecting too much the beamwidth which will be slightly wider since the efiective aperture for the array is smaller.

Non-uniform illumination of the effective aperture of the array to reduce sidelobes may also be obtained by reducing the elfective length of tubes 15 on the outer elements 12. Of course this will result in a slightly wider beamwidth since the effective apertures of the outer elements have been made smaller. Obviously, many other variations of the array may be obtained to provide numerous patterns and beamwidths. However, in all cases the operator need only move either one or both of the camming plates 28 or the tubes 15 to nonsymmertical positions wherein, for example, one side of the array produces a sharp unidirectional beam while the other side produces a plurality of sharp side lobes perpendicular thereto.

It can therefore, be seen that the antenna array being made of inexpensive, light, and largely non-metallic material and having a relatively small number of moving parts, can be easily adjusted to provide a numerous number of beam patterns and widths. Applications of this array in radar and long distance communication are unlimited and will become evident to skilled workers in the field. Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood, that within the scope of the appended claims, the invention may be practical otherwise than as specifically described.

What is claimed is:

1. An antenna array comprising a plurality of unidirec tional antenna elements, each said element comprising means for varying the effective aperture thereof, positioning means for mounting said elements in an array with each said element radiating in substantially the same general direction, and adjustable means for adjusting the spacing between each said antenna element between limits wherein said efiective apertures overlay and wherein said effective apertures are spaced from each other.

2. The antenna array according to claim 1 and further including means for varying the relative location of said eflcctive apertures along the direction of radiation.

3. The antenna array according to claim 2 and wherein said adjustable means includes means for varying the relative direction of radiation of each said antenna element between limits wherein the axis of said directions are converging and said axes are diverging.

4. Apparatus for mounting an array of antenna elements comprising a plurality of elongated antenna support rods, spaced parallel support plates having a plurality of elongated radial slots provided therein, one end of each said support rod extending through a separate one of said slots in each of said support plates, and camming means for radially sliding said rods in said radial slots.

5. Apparatus for mounting an array of antenna elements comprising a plurality of elongated antenna support rods, spaced parallel support plates having a plurality of elongated radial slots provided therein, a pair of camming plates having a plurality of spiral slots therein, each of said support plate having a separate one of said camming plates mounted adjacent and parallel thereto, said camming plates being mounted for rotation in its plane, and one end of said support rods each extending through a separate one of said spiral slots and a separate one of said radial slots in each of said support and camming plates respectively.

6. An antenna array comprising a plurality of antenna elements each including a helical radiator coaxially wound on one end of a dielectric rod and dimensioned to radiate in the axial mode, a dielectric tube slidably mounted on each said rod and mounted coaxially about the helical radiator wound thereon, and a pair of antenna positioning means, each said means comprising a pair of parallel plates, one of said plates having a predetermined number of radial positioning slots and the other of said plates having an equal number of spiral cam slots and being mounted for rotation with respect to said one of said plates, the plates of one of said positioning means being spaced from and parallel to the plates of the other of said positioning means with said radial slots on opposed plates being coextensive, the other ends of said dielectric rods each slidably extending through a separate one of said spiral slots and a separate one of said coextensive radial slots in each of said positioning means.

7. The antenna array according to claim 6 and wherein one of said dielectric rods extends through a coextensive bore provided in each of said plates along the axis of rotation of said other of said plates.

No references cited.

HERMAN KARL SAALBACH, Primary Examiner.

M. NUSSBAUM, Assistant Examiner. 

1. AN ANTENNA ARRAY COMPRISING A PLURALITY OF UNIDIRECTIONAL ANTENNA ELEMENTS, EACH SAID ELEMENT COMPRISING MEANS FOR VARYING THE EFFECTIVE APERTURE THEREOF, POSITIONING MEANS FOR MOUNTING SAID ELEMENT IN AN ARRAY WITH EACH SAID ELEMENT RADIATING IN SUBSTANTAILLY THE SAME GENERAL DIRECTION, AND ADJUSTABLE MEANS FOR ADJUSTING THE SPACING BETWEEN EACH SAID ANTENNA ELEMENT BETWEEN LIMITS WHEREIN SAID EFFECTIVE APERTURES OVERLAY AND WHEREIN SAID EFFECTIVE APERTURES ARE SPACED FROM EACH OTHER. 